(i) Field of the Invention
This invention relates to a magnetic head for magnetic recording apparatus (hereinafter referred to as "magnetic head"). More particularly, it relates to a magnetic head having a magnetic core in which two magnetic blocks of high permeability are opposed to each other with a gap intervening therebetween in its portion facing a magnetic recording medium, at least one of the magnetic blocks being made of a single-crystal ferrite.
(ii) Brief Description of the Prior Art
At the present time there is a large demand for advancing the magnetic recording technology, and especially for increasing the magnetic recording density. In complying with this demand, improvements of the recording characteristics and reproducing sensitivity of a magnetic head are important subjects, along with enhancement of the coercive force and magnetic flux density of a magnetic recording medium and reduction of noise thereof.
A magnetic head which is often used at present is as shown by way of example in FIG. 1. A magnetic core is so constructed that blocks 11 and 11' made of a high-permeability magnetic material are joined through a gap 12 so as to define a coil winding window 10. Coils 13 and 13' are wound on the magnetic core. It is generally well known that, especially when a single-crystal ferrite is employed as the high-permeability magnetic material to form the magnetic core, a magnetic head which is excellent in both high-frequency characteristics and wear resistance is obtained. Usually an Mn--Zn ferrite having a cubic structure is used as the single-crystal ferrite. Depending upon the composition of constituent elements, this ferrite exhibits a magnetic anisotropy in which the &lt;1 0 0&gt; direction or &lt;1 1 1&gt; direction is an easy axis of magnetization.
As to how the crystal axes are to be arranged in the magnetic core of the magnetic head, there is presently no established guiding doctrine because many items have not been studied yet.
It is natural that the performance of the magnetic head is dependent upon the distribution of magnetic reluctances in the magnetic core. It is difficult, however, to obtain detailed information on the situations of variations in magnetic characteristics attributed to the facing of the ferrite, especially the working of parts proximate to the gap which intensely dominate the characteristics of the magnetic head. It is very difficult to predict the working conditions of the head and the arrangment of crystal orientations under which a certain distribution of magnetic reluctances is realized. Further, even if they are predictable, it is extremely difficult, even with a current computer of high performance, to compute how the axes of magnetic anisotropy ought to be arranged in the gap portion in order to obtain the best write and read characteristics. The principal cause for the circumstances that a desirable arrangement of the crystal axes in the magnetic core is indefinite in the extreme exists, it can be said, in this point.
The following references are cited to show the state of the art:
(i) Japanese Official Patent Gazette, Patent Application Publication No. 10027/1968;
(ii) Japanese Official Patent Gazette, Patent Application Publication No. 10028/1968; and
(iii) N. Sawasaki, "VTR" (1973), pages 56 and 57, published by Corona Publishing Co., Ltd., Tokyo, Japan.